在进行轨道交通引起建筑结构振动响应计算时,为了提高高频响应的准确度,采用谱单元法(spectral element method,SEM)求解矩形楼板的动力响应,并针对既有谱单元法中板与梁(柱)单元自由度不相容问题,通过修正板的节点自由度,实现了板与梁...在进行轨道交通引起建筑结构振动响应计算时,为了提高高频响应的准确度,采用谱单元法(spectral element method,SEM)求解矩形楼板的动力响应,并针对既有谱单元法中板与梁(柱)单元自由度不相容问题,通过修正板的节点自由度,实现了板与梁、柱的耦合。将四边任意边界条件的矩形板分解为两个可以转化为类一维问题的单向板;基于Kirchhoff薄板的振动控制方程,对每一个单向板进行动力计算,并分析波的传播与横截面的振型。通过最小二乘法优化板的节点自由度,使之与梁、柱单元的自由度对应,实现谱单元法在梁板柱耦合结构中的应用。将谱单元法的计算结果与解析解和有限元法结果对比得出:在1~250 Hz内,谱单元法的计算结果比有限元准确,尤其在高频范围;谱单元模型节点数量较少,建模和计算效率高于有限元。展开更多
Self expanding metal stents (SEMS) play an important role in the management of malignant obstructing lesions in the gastrointestinal tract. Traditionally,they have been used for palliation in malignant gastric outlet ...Self expanding metal stents (SEMS) play an important role in the management of malignant obstructing lesions in the gastrointestinal tract. Traditionally,they have been used for palliation in malignant gastric outlet and colonic obstruction and esophageal malignancy. The development of the polyflex stent,which is a removable self expanding plastic stent,allows temporary stent insertion for benign esophageal disease and possibly for patients undergoing neoadjuvant chemotherapy prior to esophagectomy. Potential complications of SEMS insertion include perforation,tumour overgrowth or ingrowth,and stent migration. Newer stents are being developed with the aim of increasing technical and clinical success rates,while reducing complication rates. Other areas of development include biodegradable stents for benign disease and radioactive or drug-eluting stents for malignant disease. It is hoped that,in the future,newer stents will improve our management of these diffi cult conditions and,possibly,provide prognostic as well as symptomatic benefi t in the setting of malignant obstruction.展开更多
The effect of heat treatment on corrosion properties of CuAlNi shape memory alloy was investigated in 0.9% Na Cl solution at p H 7.4 and 37 ℃ by open circuit potential measurements, polarisation techniques, and elect...The effect of heat treatment on corrosion properties of CuAlNi shape memory alloy was investigated in 0.9% Na Cl solution at p H 7.4 and 37 ℃ by open circuit potential measurements, polarisation techniques, and electrochemical impedance spectroscopy. Investigations were performed on CuAlNi alloy samples in as-cast state and after heat treatment procedure containing annealing at 850, 885 and 920 ℃ followed by water quenching. Electrochemical impedance measurement results indicate that heat treatment of CuAlNi alloy leads to the increase in charge transfer resistance and surface layer resistance and the decrease in values of capacitance of the double and surface layers, indicating higher corrosion resistance compared with the as-cast CuAlNi alloy. The increase in polarisation resistance and the decrease in corrosion current density of heat-treated CuAlNi alloy also suggest beneficial influence of heat treatment on corrosion resistance of CuAlNi alloy. Optical microscopy, SEM/EDX and XRD analysis of samples surface after polarisation measurements show the occurrence of pitting corrosion on the electrode surfaces, with the existence of CuCl2, AlCl3 and Cu2Cl（OH）3 compounds as the surface corrosion products.展开更多
The microwave-assisted method was used to extract polysaccharides from solanum nigrum. The optimum experimental parameters, mechanism of the extraction and the effect of microwave-assisted extraction process on the st...The microwave-assisted method was used to extract polysaccharides from solanum nigrum. The optimum experimental parameters, mechanism of the extraction and the effect of microwave-assisted extraction process on the structures of polysaccharides were investigated. The extract was analyzed by the modified phenol-sulfuric acid method at 490nm. The optimum experimental parameters were obtained by orthogonal experiments as follows: extraction time 15min, microwave radiation power 455W and the process ratio of materials mass to solvent volume 1∶20. The results show that compared with the conventional reflux extraction, the microwave-assisted extraction has a higher yield in shorter time, with no effect on the finally obtained polysaccharides as seen from the FT-IR spectra. The scanning electron microscopy images reveal that the mechanism of the extraction is related to the structural changes of the plant cells in different extracting conditions.展开更多
Government regulations has great significance to establish the corresponding business rules for the market operation. However, as a ＂latent variable＂ in statistical area, government regulations has no direct method ...Government regulations has great significance to establish the corresponding business rules for the market operation. However, as a ＂latent variable＂ in statistical area, government regulations has no direct method to measure. Firstly, this paper constructs the observation indexes of government regulation at macro level. Secondly, it establishes the SEM to measure the effects of government regulation on economic development. Finally, policy implications about measuring government regulation are illustrated.展开更多
文摘在进行轨道交通引起建筑结构振动响应计算时,为了提高高频响应的准确度,采用谱单元法(spectral element method,SEM)求解矩形楼板的动力响应,并针对既有谱单元法中板与梁(柱)单元自由度不相容问题,通过修正板的节点自由度,实现了板与梁、柱的耦合。将四边任意边界条件的矩形板分解为两个可以转化为类一维问题的单向板;基于Kirchhoff薄板的振动控制方程,对每一个单向板进行动力计算,并分析波的传播与横截面的振型。通过最小二乘法优化板的节点自由度,使之与梁、柱单元的自由度对应,实现谱单元法在梁板柱耦合结构中的应用。将谱单元法的计算结果与解析解和有限元法结果对比得出:在1~250 Hz内,谱单元法的计算结果比有限元准确,尤其在高频范围;谱单元模型节点数量较少,建模和计算效率高于有限元。
文摘Self expanding metal stents (SEMS) play an important role in the management of malignant obstructing lesions in the gastrointestinal tract. Traditionally,they have been used for palliation in malignant gastric outlet and colonic obstruction and esophageal malignancy. The development of the polyflex stent,which is a removable self expanding plastic stent,allows temporary stent insertion for benign esophageal disease and possibly for patients undergoing neoadjuvant chemotherapy prior to esophagectomy. Potential complications of SEMS insertion include perforation,tumour overgrowth or ingrowth,and stent migration. Newer stents are being developed with the aim of increasing technical and clinical success rates,while reducing complication rates. Other areas of development include biodegradable stents for benign disease and radioactive or drug-eluting stents for malignant disease. It is hoped that,in the future,newer stents will improve our management of these diffi cult conditions and,possibly,provide prognostic as well as symptomatic benefi t in the setting of malignant obstruction.
基金supported by the Croatian Science Foundation under the project IP-2014-09-3405
文摘The effect of heat treatment on corrosion properties of CuAlNi shape memory alloy was investigated in 0.9% Na Cl solution at p H 7.4 and 37 ℃ by open circuit potential measurements, polarisation techniques, and electrochemical impedance spectroscopy. Investigations were performed on CuAlNi alloy samples in as-cast state and after heat treatment procedure containing annealing at 850, 885 and 920 ℃ followed by water quenching. Electrochemical impedance measurement results indicate that heat treatment of CuAlNi alloy leads to the increase in charge transfer resistance and surface layer resistance and the decrease in values of capacitance of the double and surface layers, indicating higher corrosion resistance compared with the as-cast CuAlNi alloy. The increase in polarisation resistance and the decrease in corrosion current density of heat-treated CuAlNi alloy also suggest beneficial influence of heat treatment on corrosion resistance of CuAlNi alloy. Optical microscopy, SEM/EDX and XRD analysis of samples surface after polarisation measurements show the occurrence of pitting corrosion on the electrode surfaces, with the existence of CuCl2, AlCl3 and Cu2Cl（OH）3 compounds as the surface corrosion products.
文摘The microwave-assisted method was used to extract polysaccharides from solanum nigrum. The optimum experimental parameters, mechanism of the extraction and the effect of microwave-assisted extraction process on the structures of polysaccharides were investigated. The extract was analyzed by the modified phenol-sulfuric acid method at 490nm. The optimum experimental parameters were obtained by orthogonal experiments as follows: extraction time 15min, microwave radiation power 455W and the process ratio of materials mass to solvent volume 1∶20. The results show that compared with the conventional reflux extraction, the microwave-assisted extraction has a higher yield in shorter time, with no effect on the finally obtained polysaccharides as seen from the FT-IR spectra. The scanning electron microscopy images reveal that the mechanism of the extraction is related to the structural changes of the plant cells in different extracting conditions.
文摘Government regulations has great significance to establish the corresponding business rules for the market operation. However, as a ＂latent variable＂ in statistical area, government regulations has no direct method to measure. Firstly, this paper constructs the observation indexes of government regulation at macro level. Secondly, it establishes the SEM to measure the effects of government regulation on economic development. Finally, policy implications about measuring government regulation are illustrated.
